Perfluoropolyether characterization by nuclear magnetic resonance spectroscopy and gel permeation chromatography

Karis, T. E.; Marchon, B.; Hopper, D.A.; Siemens, R.

doi:10.1016/s0022-1139(02)00197-5

Cited by 60 publications

(61 citation statements)

References 15 publications

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“…The B 2 19 F multiplet is partially overlapped with the signals of B 3 and C 3 in the 19 F 1D-NMR spectrum; therefore, the 2 J CF HSQC spectrum Fig. 8(j) shows correlations from carbon B 1 to both fluorine B 2 and B 3 .…”

Section: Units B and Cmentioning

confidence: 98%

“…The 19 F 1D-NMR of Krytox  fluoropolymer is usually dispersed into three regions where the CF 3 Typical J coupling values between 19 F and X nuclei are summarized in Table 1. The one-and two-bond 19 F- 13 C couplings in these fluoropolymers normally fall around 250-310 and wileyonlinelibrary.com/journal/mrc 30-50 Hz, respectively.…”

Section: F-f Selective Cosy 2d-nmrmentioning

confidence: 99%

“…B 3 and C 3 are the trifluoromethyl groups on the B and C repeat units, respectively. Both their 19 F and 13 C shifts are similar and appear as a single correlation in the 2D-HSQC spectrum Fig.…”

Section: Units B and Cmentioning

confidence: 99%

“…While the commercial use of PFPEs is over 50 years old, new knowledge about their compositions continues to be discovered, yet reports in the literature of thorough structure characterization are limited. The chain-end structures of PFPEs have been the subject of a nuclear magnetic resonance (NMR)/gel permeation chromatography (GPC) investigation, [3] the decarboxylation of oligomeric chain-end carboxylate salts have been studied, [4] and the syntheses of various chain-end terminated polymers have been studied. [5,6] The mechanism of high temperature radical decarboxylation has been examined in some detail using GC-MS analysis and by comparison of the 13 C NMR spectra of the polymer product mixture with spectra of model compounds.…”

Section: Introductionmentioning

confidence: 99%

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2D‐NMR studies of a model for Krytox^® fluoropolymers

McCord

Baiagern

et al. 2011

Magnetic Reson in Chemistry

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Multiple two-dimensional nuclear magnetic resonance (2D-NMR) techniques have been used to study the structures of Krytox(®) perfluoro(polyalkyl ether) and its mechanism of polymerization. Model compound K(4), containing four Krytox(®) fluoropolymer repeat units, was analyzed to interpret the multiplet patterns in the NMR spectra from the polymer model. (19)F {(13)C}-Heteronuclear single-quantum correlation experiments, performed with delays optimized for (1)J(CF) and (2)J(CF), provided spectra that permitted identification of resonances from individual monomer units. Selective, (19)F-(19)F COSY 2D-NMR experiments were performed with different excitation regions; these experiments were combined with selective inversion pulses to remove (19)F-(19)F J couplings in the f(1) dimension. The resulting COSY spectra were greatly simplified compared with standard (19)F-(19)F COSY spectra, which are too complicated to interpret. They give information regarding the attachments of monomer units and also provide insights into the nature of the stereoisomers that might be present in the polymer. Both infrared and NMR spectra show peaks identifying chain end structures. With the help of these studies, resonances can be assigned, and the average number of repeat units in the polymer chain can be calculated based on the assignments obtained.

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Section: Units B and Cmentioning

confidence: 98%

Section: F-f Selective Cosy 2d-nmrmentioning

confidence: 99%

Section: Units B and Cmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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2D‐NMR studies of a model for Krytox^® fluoropolymers

McCord

Baiagern

et al. 2011

Magnetic Reson in Chemistry

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“…The temperature for the calculations is 35°C and the lubricant is Zdol. The relationship between Zdol vapor pressure and molecular weight is from thermal gravimetric measurements [8,15] at 35°C. Its viscosity at 35°C is from the measurements with a capillary viscometer [8].…”

Section: Parameters For the Calculation Of Lubricant Transfer And Accmentioning

confidence: 99%

Dominant Factors in Lubricant Transfer and Accumulation in Slider-Disk Interface

Liu

2007

Tribol Lett

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Lubricant transfer from disk to slider and lubricant accumulation on slider are very important in designing a stable slider-disk interface of ultra-low spacing. In this article, the effects of different parameters on the lubricant transfer and accumulation are studied and the reasons behind the effects are explained. Furthermore, the time for the lubricant transfer to reach steady state is estimated. It is found that lubricant molecular weight plays a dominant role in the lubricant transfer and accumulation. Lubricant transfer and accumulation decrease dramatically with the increase in lubricant molecular weight. Lubricant transfer also strongly depends on lubricant thickness and bonding ratio on disk surface. A thinner lubricant and higher lubricant bonding ratio on disk surface reduce lubricant transfer obviously, which results in less lubricant accumulation. A diamond-like-carbon (DLC) overcoat of low adsorption area density on slider surface can reduce lubricant transfer and accumulation, especially for lubricant of low molecular weight. Lubricant accumulation increases with disk velocity and increases slightly with the decrease in slider flying height. Lubricant accumulation can be reduced by minimizing the area of slider pad. Lubricant transfer and accumulation become worse at higher ambient temperature. It takes seconds for lubricant of low molecular weight to reach steady transferred thickness and hours for lubricant of high molecular weight to reach the steady state.

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